A well known and widely used construction for securing sheaves, pulleys, sprockets, couplings, and the like to rotatable shafts consists of a split, tapered bushing disposed around the shaft, with the body of the bushing disposed between the shaft and the hub of one of the driving or driven elements mentioned above. The hubs normally have a tapered inner surface which corresponds to the tapered outer surface of the bushing. One particular type of bushing used for this purpose has a flange disposed around the outside and adjacent the body or barrel of one end of the bushing with a plurality of threaded bores therein for securing the bushing to the hub. Screws are inserted through the flange into corresponding threaded bores in the hub and, as the screws are tightened, the tapered surfaces of the bushing and hub are drawn together. This, in turn, causes the split bushing to contract around and securely grip the shaft, thereby securing the assembly together and preventing relative rotation between the shaft, bushing, and hub. Reverse mounting is also possible where, for example, there is limited space adjacent the flanged end of the bushing. In this case, screws are inserted through unthreaded holes in the hub, and into corresponding threaded bores in the flange. As the screws are tightened, the tapered surfaces are drawn together and the bushing contracts around the shaft as described above.
In many installations, a key with a corresponding keyway is provided between the shaft and the bushing and/or between the bushing and the hub to further guard against relative rotation between the members. The bushings are normally produced either by machining the bushings from blanks of cast iron, or by a powdered metal process which eliminates much of the machining required in producing the bushing from the cast iron blanks.
In normal use, the bushings are often subjected to very high torque, especially where frequent reversal of rotation is effected. Any loosening of the secured elements becomes progressively worse as operations proceed, due to the pounding between the parts, and may ultimately result in damage to one or more of the elements. In addition, fatigue stresses are concentrated in certain areas of the bushings, specifically the fillets or junctions between the flange and the barrel, and the fillets between the key and the barrel. Past efforts to overcome these difficulties have been concentrated either on reinforcement of the areas subject to stress, resulting in increased weight and manufacturing expenses, or on designing the bushings to permit a certain amount of flexing, reducing the stress concentration but resulting in an overall weakening of the bushing structure.